Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the ...Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin（Ⅱ） metallocene complexes LSn R（L = HC[CMe（N-2,6-iPr2C6H3）]2,R = cyclopentadienyl,C5H5（1）; indenyl,C9H7（2）; fluorenyl,C（13）H9（3）） stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C（C5 ring） bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature（25~–75 ℃） ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin（Ⅱ） atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C（C5 ring） bond modes appear influenced by either the metallocene size or the compound state existed.展开更多
Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used...Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used NaOH-EDTA extraction and solution ^31P nuclear magnetic resonance （NMR） spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase （AcP）, phosphodiesterase （PD） and inorganic pyrophosphatase （IPP）, in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients （i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m）. The results show that total P （TP）, organic P （OP）, OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP （73%0-83%） with a large proportion of monoesters （65%0-72%）, whereas inorganic P is present in lower proportions （17%-27%）. The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon （TC）, total nitrogen （TN）, and TP （P 〈 0.05）, indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.展开更多
Current resolved structures of GPCRs and G protein complexes provided important insights into G protein activation. However, the binding or dissociation of GPCRs with G protein is instantaneous and highly dynamic in t...Current resolved structures of GPCRs and G protein complexes provided important insights into G protein activation. However, the binding or dissociation of GPCRs with G protein is instantaneous and highly dynamic in the intracellular environment. The conformational dynamic of G protein still needs to be addressed. In this study, we applied ^(19)F solution NMR spectroscopy to monitor the conformational changes of G protein upon interact with detergent mimicking membrane and receptor. Our results show that there are two states equilibria in the G_(α)in apo states. The interaction of G_(α)with detergents will accelerate this conformational transformation and induce a state that tends to bind to GPCRs. Finally, the G_(α)proteins presented a fully activation state when they coupled to GPCRs.展开更多
基金supported by the National Natural Science Foundation of China(21473142 and 21673191)the National Innovative Research Team of China(IRT_14R31 and J1310024)
文摘Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin（Ⅱ） metallocene complexes LSn R（L = HC[CMe（N-2,6-iPr2C6H3）]2,R = cyclopentadienyl,C5H5（1）; indenyl,C9H7（2）; fluorenyl,C（13）H9（3）） stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C（C5 ring） bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature（25~–75 ℃） ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin（Ⅱ） atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C（C5 ring） bond modes appear influenced by either the metallocene size or the compound state existed.
基金National Natural Science Foundation of China(No.41171241)
文摘Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used NaOH-EDTA extraction and solution ^31P nuclear magnetic resonance （NMR） spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase （AcP）, phosphodiesterase （PD） and inorganic pyrophosphatase （IPP）, in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients （i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m）. The results show that total P （TP）, organic P （OP）, OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP （73%0-83%） with a large proportion of monoesters （65%0-72%）, whereas inorganic P is present in lower proportions （17%-27%）. The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon （TC）, total nitrogen （TN）, and TP （P 〈 0.05）, indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.
基金supported by the National Key Research and Development Project of China (Nos.2019YFA0904100 and 2017YFA0505400)the National Natural Science Foundation of China (Nos.22077117 and 31971152)the USTC Research Funds of the Double First-Class Initiative。
文摘Current resolved structures of GPCRs and G protein complexes provided important insights into G protein activation. However, the binding or dissociation of GPCRs with G protein is instantaneous and highly dynamic in the intracellular environment. The conformational dynamic of G protein still needs to be addressed. In this study, we applied ^(19)F solution NMR spectroscopy to monitor the conformational changes of G protein upon interact with detergent mimicking membrane and receptor. Our results show that there are two states equilibria in the G_(α)in apo states. The interaction of G_(α)with detergents will accelerate this conformational transformation and induce a state that tends to bind to GPCRs. Finally, the G_(α)proteins presented a fully activation state when they coupled to GPCRs.
